Evidence Law in Japan

Foundational Sources and Structure

Japanese evidence law derives from two principal codes: the Code of Criminal Procedure (Keiji Sosho Ho, Act No. 131 of 1948) and the Code of Civil Procedure (Minji Sosho Ho, Act No. 109 of 1996). The criminal evidence regime was heavily shaped by American occupation legal reforms (1945–1952), creating a hybrid adversarial-inquisitorial framework. The Constitution establishes fundamental evidentiary principles: Article 38(1) guarantees the privilege against self-incrimination; Article 38(2) establishes the exclusionary rule for coerced confessions; Article 38(3) requires corroboration (no conviction solely on confession); and Article 37 guarantees the right to confront witnesses and compulsory process.

Criminal Evidence: Presumptions and Burden of Proof

The presumption of innocence is the foundational principle of Japanese criminal evidence. The prosecution bears the burden of proof beyond a reasonable doubt. In the Kanezawa Case (Supreme Court, 1975), the Court articulated the standard as requiring that “evidence must establish guilt to the extent that any reasonable doubt is excluded.” The burden never shifts to the accused. The corroboration requirement under Article 319(2) CCP prohibits conviction solely on a confession — elaborated in the Shimane Case (Supreme Court, 1949), requiring independent evidence establishing the corpus delicti and connecting the defendant to the crime. The rule applies whether the confession is voluntary or not.

Hearsay Rule in Criminal Proceedings

Japan’s hearsay rule, codified in Articles 320–328 CCP, was influenced by Anglo-American doctrine but operates with significant differences. Article 320 establishes the general rule: out-of-court statements are inadmissible to prove the truth of the matter asserted unless an exception applies. Article 321 governs written statements: subsection (1)(i) admits sworn statements before a judge where the declarant is unavailable; subsection (1)(ii) admits prior testimony records under confrontation conditions; subsection (1)(iii) governs sworn statements before a prosecutor, admissible if the declarant testifies and is cross-examinable, or is unavailable due to death, incapacity, disappearance, or residence abroad — subject to a “special circumstances” reliability requirement. Article 322 permits admission of the defendant’s own statements subject to voluntariness and corroboration review. Article 323 provides exceptions for business records, official records, and routinely created documentary evidence. The dying declaration and declaration against interest exceptions have been recognized through judicial interpretation.

Disclosure and Discovery in Criminal Proceedings

Japan’s criminal discovery regime, reformed by 2005 amendments and 2016 plea bargaining provisions, operates on a three-tier classification: Type I (evidence the prosecutor intends to present at trial), Type II (statutorily specified categories including exculpatory evidence), and Type III (materials related to proposed witness testimony). Type I disclosure is triggered by the defendant’s request; Type II and III obligations are more limited and have generated extensive litigation over prosecutorial discretion. The 2016 amendments introduced plea bargaining (keiji kōshō), allowing charge reduction in exchange for cooperation in organized crime, corruption, and financial offense investigations.

Expert Evidence

Expert evidence in criminal proceedings is governed by Article 321(4) CCP. Reflecting the civil law tradition, experts are formally court-appointed (kanteinin) rather than party-selected, submitting written opinions examined by the parties at trial. Parties may present their own expert reports, though these are subject to hearsay restrictions. Japanese courts apply a deferential standard for scientific evidence, generally admitting expert testimony on a showing of relevance and reliability without a formal Daubert or Frye gatekeeping standard — a stance criticized in cases involving DNA, psychiatric evaluation, and forensic fire investigation.

Civil Evidence: Documentary Evidence and Free Evaluation

Civil evidence is governed by the Code of Civil Procedure, which establishes the principle of free evaluation of evidence (Article 247 CCP): the court determines probative value according to its free discretion, subject to logic and experience. Documentary evidence (shōsho) is the dominant form of proof. The CCP establishes obligations to produce documents (Article 220, subject to privilege and self-incrimination exceptions), procedures for challenging authenticity, and presumptions regarding notarized documents. Authentication under Articles 228–229 CCP requires proof of a private document’s authenticity through handwriting, seal impression, or other means, while notarial documents are presumed authentic. The pervasive use of personal seals (hanko or inkan) means seal impression evidence (in’ei kantei) plays a distinctive role, often determinative in authenticity disputes.

Witness Testimony and Party Examination

Witness testimony in civil cases (Articles 190–206 CCP) obligates witnesses to testify, subject to recognized privileges: close relatives, professional confidentiality (attorneys, physicians, clergy), state secrets, and self-incrimination. The court examines witnesses first (civil law tradition), followed by cross-examination. Party examination (Articles 207–211 CCP) permits the court to examine the parties, and a refusal without legitimate grounds permits adverse inferences.

Disclosure in Civil Proceedings

Japan’s civil discovery regime is more limited than that of the United States but was expanded by the 1996 reforms. The CCP establishes a document production order system (Article 220) requiring a party to produce specified documents, subject to enumerated exceptions. The 2003 introduction of pretrial case management (shinri no keikaku) allows the court to establish discovery schedules and order early evidence disclosure. Nevertheless, civil discovery remains court-supervised and limited to issues identified in the pleadings, reflecting the system’s commitment to judicial case management over party-driven discovery.